package com.seek.util;

import java.util.HashMap;

public class MyHashMap extends HashMap {
	
	
	 @Override  
	    public Object put(Object key, Object value)  
	    {  
	        //如果已经存在key，不覆盖原有key对应的value  
	        if(!this.containsKey(key))  
	            return super.put(key, value);  
	          
	        return null;  
	    }  

}
